1. Field of the Invention
The present invention relates to a method and an apparatus for obtaining arrangement information of indices and a sensor both placed on and relative to an object.
2. Description of the Related Art
By setting a plurality of indices on a measuring object; capturing the measuring object with a camera; and detecting the image coordinates of the projected figure of each index in the captured image, the position and the orientation of the measuring object relative to the camera or in the space having the camera installed therein are obtained (see, e.g., D. G. Lowe, “Fitting Parameterized three-dimensional models to images”, IEEE Transactions on PAMI, vol. 13, no. 5, pp. 441-450, 1991 (hereinafter “Lowe”), and A. I. Comport, E. Marchard, F. Chaumette: “A real-time tracker for markerless augmented reality”, Proc. Int'l Symp. On Mixed and Augmented Reality 2004, pp. 36-45, 2004 (hereinafter “Comport et al.”).
In K. Satoh, S. Uchiyama, and H. Yamamoto: “A head tracking method using bird's-eye view camera and gyroscope”, Proc. 3rd IEEE/ACM Int'l Symp. on Mixed and Augmented Reality (ISMAR 2004), PP. 202-211, 2004 (hereinafter “Satoh et al.”), a method for measuring the position and the orientation of an object is proposed. In this method, indices and an orientation sensor are placed on a measuring object, and an objective-viewpoint camera is placed to observe the measuring object at an objective (third-person) viewpoint. The position and the orientation of the object are measured on the basis of figures of the indices detected from an image captured by the objective-viewpoint camera, and an orientation-measurement value of an orientation sensor. As for the case where an imaging device is a measuring object, a method has been proposed for measuring the position and the orientation of an object (by a group including the inventors of the present invention and others). In this method, indices and an orientation sensor are placed on an imaging device, an objective-viewpoint camera is placed to observe the imaging device, and other indices are arranged in a scene to be observed by the imaging device. The position and the orientation of the imaging device are measured on the basis of figures of the indices on the imaging device detected from an image captured by the objective-viewpoint camera; figures of the indices in a scene detected from an image captured by the imaging device itself; and an orientation-measurement value of an orientation sensor.
Regarding the method in which the position and the orientation of a measuring object are computed by detecting figures of a plurality of indices set on the object, the positional relationship between the indices and the object must be previously known. In the case where an orientation sensor is used for measuring the position and the orientation of an object as set forth in Satoh et al., the orientation of the orientation sensor relative to the measuring object must be previously known.
Hitherto, works for obtaining these positional relationships, i.e., two kinds of arrangement information of the indices and the sensor relative to the object, are independently conducted (hereinafter, a work generally referred to as calibration). That is, two kinds of calibration of an index and an orientation sensor are conducted in mutually different steps. Unfortunately, mutually independent calibration of them causes troublesome works.